Physiological events give rise to physiological signals or themselves represent signals, on the basis of which they can be classified. The classification of physiological events or signals is useful in particular in relation to implantable medical devices such as for example cardiac pacemakers or implantable defibrillators in order to distinguish events requiring treatment from those which are not in need of treatment, or events in respect of which different treatments are indicated. On the basis of the classification procedure the implantable medical device is put into the position of automatically triggering off the treatment which is possibly required.
Previous apparatuses for the classification of physiological events, in particular intracardial events, in implantable medical devices are essentially based on filtering of the signal shape and on the provision of a threshold value or a plurality of threshold values in combination with time analysis in respect of the value exceeding/falling below the threshold value or values.
In order to achieve acceptable sensitivity to the signals of physiological events and acceptable distinguishability of events with the known apparatuses, it is necessary, during the cardiac cycle in which an event occurs, to suspend the recording of further physiological signals. However such suspension excludes the reliable detection of various important classes of intracardial events and the effective treatment thereof, thus for example an abnormal relationship between the two chambers of the heart.
Therefore the object of the present invention is to provide an improved apparatus for the classification of physiological events, in particular intracardial events, which helps to overcome the above specified disadvantages.